Book Image

Learn Kotlin Programming - Second Edition

By : Stephen Samuel, Stefan Bocutiu
Book Image

Learn Kotlin Programming - Second Edition

By: Stephen Samuel, Stefan Bocutiu

Overview of this book

Kotlin is a general-purpose programming language used for developing cross-platform applications. Complete with a comprehensive introduction and projects covering the full set of Kotlin programming features, this book will take you through the fundamentals of Kotlin and get you up to speed in no time. Learn Kotlin Programming covers the installation, tools, and how to write basic programs in Kotlin. You'll learn how to implement object-oriented programming in Kotlin and easily reuse your program or parts of it. The book explains DSL construction, serialization, null safety aspects, and type parameterization to help you build robust apps. You'll learn how to destructure expressions and write your own. You'll then get to grips with building scalable apps by exploring advanced topics such as testing, concurrency, microservices, coroutines, and Kotlin DSL builders. Furthermore, you'll be introduced to the kotlinx.serialization framework, which is used to persist objects in JSON, Protobuf, and other formats. By the end of this book, you'll be well versed with all the new features in Kotlin and will be able to build robust applications skillfully.
Table of Contents (21 chapters)
Free Chapter
1
Section 1: Fundamental Concepts in Kotlin
5
Section 2: Practical Concepts in Kotlin
15
Section 3: Advanced Concepts in Kotlin

Type inference

Did you notice, in the previous section, that the type of the variable was not included when it was initialized? This is different to Java where the type of the variable must usually accompany its declaration. From Java 11 onward, local variables can also omit the type, but fields must always be annotated with the type.

Even though Kotlin is a strongly typed language, we don't always need to declare types explicitly. The compiler attempts to figure out the type of an expression from the information included in the expression. A simple val variable is an easy case for the compiler because the type is clear from the right-hand side. This mechanism is called type inference. This reduces boilerplate code, whilst keeping the type safety we expect of a modern language.

Values and variables are not the only places where type inference can be used. It can also be used...